The antennas
The installation on the roof-top comprises
- at right: two 14-element crossed Yagi-Uda antennas for the Amateur Radio 144 MHz band, vertically stacked at 1.15 wavelength. Each antenna has a gain of 12.3 dBi; the stacked combination will have about 15.3 dBi gain. There is a mast-head preamplifier with a noise figure of 0.9 dB and a gain of 20 dB.
- at left: two 30-element crossed Yagi-Uda antennas for the Amateur Radio 432-440 MHz band, vertically stacked at 2 wavelengths separation. Each antenna has a gain of 16.3 dBi; the combination about 19.3 dBi. The mast-head preamplifier has a noise figure of 0.9 dB and a gain of 20 dB.
- centre: a 60cm diameter parabolic dish for the 2400 MHz Amateur Radio satellite band with 21 dBi gain. In the focus there is a 1.3dB noise figure convertor which brings the signal down to 144 MHz intermediate frequency.
The coaxial cables
The distance of 45m between antennas on the roof and the transceiver in the control room is covered by low-loss coaxial cables for the radio signals. Thus, there is some attenuation which amounts to
- 1.5 dB on 144 MHz
- 2.5 dB on 432 MHz
- there may be further losses by the cables making sharp bends in some places, the cable connectors, and by an in-line SWR-meter
Control Room Equipment
Apart from the computers (not shown) which can completely control the equipment, the station consists of a Icom IC910H Amateur Radio Transceiver (centre) and the controllers for the azimuth (left bottom) and elevation rotators. Also, there is a switch to change-over the handedness of the circular polarization of the antennas' radiation. Of course, all equipment can also be operated manually.
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last update: Apr. 2013 J.Köppen